Humidification Degree Effect under Rain of Inclined Silicone Insulation on its Electric Performance

Abstract

This investigation is focused on the effect of inclination angle with respect to the horizontal of a hydrophobic silicone insulation, on the rate of its creepage distance's wetting by natural rain. The constellation of rainwater drops obtained on the de-energized site is then reproduced in the laboratory, to quantify the effect of their volume on the humidification intensity of the inclined insulation's creepage distance, and therefore its electrical performance under different alternating voltage levels. For this purpose, two different experimental devices allowing the variation of the insulation's inclination angle were set-up. The first one is dedicated to the on-site display of silicone samples in natural rain. The second one allows the study of the applied voltage's effect on the wetting degree of the insulation's surface. All the performed tests were supported by camera visualization. On-site measurement results show a decline in the length of the creepage distance of the natural rain-wetted insulation with increasing its inclination angle. Laboratory results also show a decrease in the size of the insulation's wet surface with increasing its inclination angle. These two characteristics reveal two different intervals of critical inclination angles of the insulation, unfavorable and favorable, for the dimensioning of the insulators' sheds corresponding respectively to their minimum and maximum electrical performance.